The present invention relates to a milk beverage, and more particularly, to a milk beverage which is excellent in emulsion-thermal stability and long-term keeping stability even when the beverage is subjected to UHT sterilization ordinarily used for PET bottle-filled beverages.
Milk beverages containing milk components, such as milk coffee, have been subjected to heat sterilization treatment upon the production thereof for subsequent storage. In order to prevent deterioration or putrefaction of these milk beverages due to growth of surviving thermophilic spore bacteria having a heat resistance, it is widely known to add sucrose fatty esters thereto. There have also been proposed methods of using polyglycerol fatty acid ester in combination with sucrose fatty acid ester in order to prevent liberated fats or coagulated proteins from being produced during storage of milk beverages, and to maintain a good emulsion stability of the milk beverages for a long period of time (Japanese Patent Application Laid-Open (KOKAI) Nos. 61-2426567(1986) and 62-215345, etc.). These methods are very effective to maintain the emulsion stability of milk beverages.
The above conventional methods are applicable to retort-sterilized milk beverages without problem, but do not have sufficient effects on milk beverages which are subjected to UHT (ultra high temperature) sterilization recently used for PET bottle-filled beverages. This is because when being subjected to UHT sterilization, milk proteins contained in the milk beverages are thermally denatured and tend to be precipitated, resulting in deterioration in keeping property thereof. To solve this problem, there has been further proposed the method of minimizing the UHT sterilization time and adding polysaccharides as a thickener such as pectin or carrageenan to the milk beverages. However, this method is still insufficient to allow the UHT-sterilized milk beverages to maintain its keeping stability for a long period of time.
As a result of the present inventors' earnest studies, it has been found that a milk beverage containing a polyglycerol fatty acid ester having a specific cloud point exhibit a good emulsion stability for a long period of time even when being subjected to UHT sterilization. The present invention has been attained on the basis of the finding.